Two-A-Days: When and How to Run Doubles

How to use two-a-days (doubles) in training for an ultramarathon.

By on September 6, 2023 | Comments

I was first introduced to two-a-days, also known as doubles, in high school, though I wasn’t the one doing them — our top runner was. He hadn’t trained enough over the summer and this was our coach’s method of getting him in shape quickly before the crucial end-of-season races. In just three months, the team witnessed the transformation from him in off-season fitness to one of the top runners in the state. At that point in my running career, I couldn’t fathom the notion of running twice in one day. However, this certainly showed me that it could work wonders under the right circumstances.

Two-a-days refers to completing two workouts in the same day. One of the two runs is usually shorter and easier in effort. Side note: Unlike 99.9% of us, some elite runners have been known to run two difficult sessions in a day during their peak conditioning. Called double threshold training, this training principle is utilized by the best of the best to add hard, quality work into a day without overdoing it during any single workout. For the purposes of this article, we’ll omit how this 0.01% trains.

Running doubles

Photo: iRunFar/Eszter Horanyi

There are Two Purposes to Two-A-Days

  1. Recovery — A short session of jogging several hours following a tough stamina-based workout or speed-based workout is a form of active recovery. It helps flush the wastes accumulated in the legs and can be used to warm the body before a foam roller or stretching session.
  2. Endurance Improvement — The day’s additional run acts as an endurance-based workout by training the body to become efficient at burning fat and storing muscle glycogen, increasing the size and number of muscle capillaries and mitochondria, and teaching the body and mind to keep going when fatigued.

Who Should be Running Doubles?

  1. Established high mileage ultrarunners who consistently run more than 75 miles or 10 to 12 hours a week.
  2. Those who are physically prepared to increase their weekly volume. Runners who have steadily improved their fitness through single-run-per-day workouts, but have reached a performance plateau.
  3. Runners with limited days of the week or short windows of opportunity to train, such as firefighters and individuals in the medical field.

Who Should Avoid Two-A-Days?

Runners who have a history of or currently battle injury should avoid running twice a day. Athletes who succumb to injury easily but are looking to improve on their endurance with the use of a second daily workout should invest their time safely with non-impact aerobic activities like cycling, elliptical trainers, swimming, and Alter-G treadmills.

Implementing Doubles into Your Run Training

  1. Those who’ve never run twice per day should start with one or two second runs during the week and, if all goes well, slowly build to three or four per week in as many months.
  2. Second runs can be done morning, afternoon, or evening, but they should be timed so that ample recovery can occur before or after the primary workout. When first starting out, avoid performing second runs on days that are recovery focused.
  3. The distance of the second session can vary greatly. Twenty minutes is enough to get the blood flowing and warm the muscles, while 60 minutes is plenty in order to build endurance. Again, ensure that the distance of these second runs doesn’t impact the following day’s workout.
  4. Whether your ultra takes you to the road, trail, mountains, or beach, you should keep these second runs as simple as possible. Avoid adverse weather conditions and run at an easy pace on soft, flat surfaces.

Two-a-day workouts are a relatively safe way to increase your mileage, improve your fitness, and work around a busy schedule.

As an extreme example, in 1994, while working full time, David Horton was able to fit in three workouts a day to prepare his body and mind for the Trans-American Footrace, an approximately 3,500-mile coast-to-coast event. Horton explains, “I was running three times a day during the week; in the morning, some at noon, and then some after work. I averaged 180 miles per week for two months, with the biggest training week being 193 miles. This training readied me for the Trans-Am, even though during the race we averaged 315 miles per week. That was 45 miles per day for nine weeks at 9:15-minutes-per-mile pace.”

Call for Comments

  • Have you ever used two-a-days in your training?
  • Do you think they benefited your fitness?

[Editor’s Note: As one of iRunFar’s best training articles, we’ve worked with author Ian Torrence to update this article before resharing it.]

Running two-a-days

Photo: iRunFar/Eszter Horanyi

Ian Torrence

Ian Torrence has more than 12 years of experience coaching runners of all levels. Ian has completed more than 220 ultramarathons, with 50+ wins, since his first ultra finish at the 1994 JFK 50 Mile. Ian and his wife, Emily, are online coaches at Sundog Running. Information about his coaching services can be found at